1. Field of the Invention
The present invention relates to an air passage switching system having a door for opening and closing an air passage through which air flows. The air passage switching system is suitable for an air outlet mode switching unit for a vehicle air conditioner.
2. Related Art
A conventional air passage switching system for an air conditioner of a vehicle has an air conditioning case for forming an air passage, and a butterfly door for switching the air passage. A rotation shaft for rotating the butterfly door is disposed at side end centers of the door. The butterfly door is rotatably held in the air conditioning case to be rotated by the rotation shaft. The butterfly door includes a door body portion made of resin having a high rigidity, and a lip-seal like seal member made of an elastomer. The seal member is formed into a thin-plate like (i.e., flat sheet) integrally with the door body portion on the outer peripheral portion of the door body portion. However, because the seal member is formed into the thin-plate like to have a low rigidity, the seal member is readily deformed due to inner shrinking force, and is readily bent upwardly on a corner portion. To prevent this problem, when a seal member 202 is formed into a lip like having a T-shaped or Y-shaped end section around a door body portion 200 as shown in FIGS. 15A, 15B, the rigidity of the seal member 202 is increased, and the seal member 202 is not readily deformed. However, it is compared with the seal member formed into a thin-plate like, the T-shaped or Y-shaped end section is difficult to be molded, and the producing cost of the seal member 202 is increased. Further, the thickness of the top end of the seal member 202 becomes larger due to the T-shaped or Y-shaped end section, an area of an air passage is reduced and pressure loss of the air passage is increased when the door is opened.